Communication system, communication device, wired communication device, and communication method

ABSTRACT

A communication system includes a wired communication device and a communication device that can communicate with a wireless communication device and the wired communication device. The communication device includes a clock output unit and a modulator. The wired communication device includes a clock extracting unit, a signal extracting unit, and a processing unit. The communication device and the wired communication device are connected to each other by a first connecting line through which a modulated signal is sent from the communication device to the wired communication device, and a second connecting line, which is different from the first connecting line, through which a signal is sent from the wired communication device to the communication device.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/369,795, filed Mar. 6, 2006, which claims priority toJapanese Patent Application JP 2005-062418 filed in the Japanese PatentOffice on Mar. 7, 2005, the entire contents of which are incorporatedherein by reference.

BACKGROUND

The present disclosure relates to communication systems, communicationdevices, wired communication devices, and communication methods. Moreparticularly, the disclosure relates to a communication system, acommunication device, a wired communication device, and a communicationmethod that can perform wired communication with a simple configurationof the devices by minimizing the number of lines for connecting thedevices.

Integrated circuit (IC) cards that can perform near field communication,which is one type of wireless communication, are coming into widespreaduse because of its utility. Such IC cards that perform near fieldcommunication are used in, for example, an automatic ticketing system ina station or an electronic settlement system that conducts settlement byusing e-money.

Due to the spread of near field communication IC cards, thestandardization of near field communication protocols that can be usedby IC cards is in progress. A typical example of such communicationprotocols is Near Field Communication Interface and Protocol (NFCIP)-1,which is defined as ISO/IEC18092.

NFCIP-1 defines two communication modes, i.e., an active mode and apassive mode. In the active mode, to send data, a plurality ofcommunication devices each output electromagnetic waves and modulatethem by themselves. In the passive mode, to send data, one of aplurality of communication devices outputs electromagnetic waves andmodulates them, and another communication device receives theelectromagnetic waves and performs load modulation on them.

Communication devices based on NFCIP-1 perform communication either inthe active mode or the passive mode (see, for example, JapaneseUnexamined Patent Application Publication No. 2004-215225 and“Information Technology Telecommunications and Information Exchangebetween Systems Near field Communication Interface and Protocol(NFCIP-1)”, First Edition 2004 Apr. 1, ISO/IEC18092:2004(E)).

In addition to IC cards, cellular telephones are now widely used, and adevice integrating an IC card and a cellular telephone therein, i.e., acellular telephone having a built-in IC card that performs near fieldcommunication, is already put to practical use. More precisely, acellular telephone integrates an IC chip rather than an IC card therein,that is, the shapes of the IC card and the IC chip are differentalthough the functions thereof are similar. For the convenience ofdescription, however, IC chips having functions similar to those of ICcards are also referred to as “IC cards”.

Some cellular telephones are designed to allow users to install andremove subscriber identity module (SIM) cards (which include SIM chips)storing subscriber information (for example, telephone numbers)necessary for the users to use the cellular telephones. Such cellartelephones are hereinafter referred to as “SIM-compatible cellulartelephones”.

If the user replaces a currently used SIM-compatible cellular telephoneby another SIM-compatible cellular telephone, he/she can remove the SIMcard from the old one to insert it into the new one to use the newcellular telephone.

As the standards superior to SIM, user identity module (UIM) isavailable. UIM cards (which include UIM chips) can handle, not only usersubscriber information, but also personal information, such as creditcard numbers and authentication information used for conductingauthentication. SIM cards and UIM cards are defined in ISO7816.

SIM cards or UIM cards have terminals (pins) for performing wiredcommunication with other devices to send and receive signals. When a SIMcard or a UIM card is installed in a cellular telephone, the terminalsof the SIM card or the UIM card are brought into contact with theterminals of the cellular telephone so that the circuit in the cellulartelephone can send and receive signals to and from the SIM card or theUIM card by wired communication.

It is necessary that SIM cards or UIM cards be small since they areinstalled in portable machines, such as cellular telephones.Accordingly, only a small number of terminals, for example, about 8terminals, are provided for sending and receiving signals to and fromother devices, and some of the terminals are used for sending andreceiving signals to and from the circuit in a cellular telephone.

As discussed above, currently, there are two types of cellulartelephones, i.e., one type of which has a built-in IC card that performsnear field communication, and the other type of which allows users toinstall and remove SIM cards or UIM cards (hereinafter simply referredto as “SIM cards”). It can be therefore expected that cellulartelephones having built-in IC cards that perform near fieldcommunication and are compatible with SIM cards will be put to practicaluse and become popular.

In such cellular telephones, a communication interface used forperforming near field communication by using an IC card is probably usedfor sending and receiving signals between a built-in SIM card andexternal devices.

In this case, it is necessary that such a near field communicationinterface be connected with the SIM card by physical lines (wires).

As stated above, however, only a small number of terminals are providedfor the SIM card and some of them are already used. Accordingly, it isnecessary to minimize the number of physical lines for connecting thenear field communication interface with the SIM card.

On the other hand, if the number of lines is reduced, it is necessarythat signals be sent and received with such a small number of lines,which increases the complexity of the communication interface and theSIM card.

More specifically, if signals are sent from the communication interfaceto the SIM card and also from the SIM card to the communicationinterface by using only one connecting line, it is necessary to changethe impedance (impedance when viewed from an external source) in thecommunication interface or the SIM card between when a signal is sentand when a signal is received. Impedance changes further change voltagesor currents, in which case, the detection of signals (for example,detecting the levels of received signals) should be performed byprecisely considering such voltage or current changes. Additionally,when the SIM card is installed in a cellular telephone, the impedancewhen viewed from one of the communication interface and the SIM card tothe other one may be changed depending on the condition of contactbetween the terminals of the cellular telephone and those of the SIMcard. It is thus necessary to design the communication interface and theSIM card to cope with the above-described impedance changes or voltageor current changes. Thus, the configuration of the communicationinterface and the SIM card become complicated.

As the configuration of the communication interface or the SIM cardbecomes complicated, the size thereof is also increased. This is notpreferable since the communication interface and the SIM card, inparticular, the SIM card, should be small, as discussed above.

SUMMARY

It is thus desirable to perform wired communication between a wiredcommunication device, such as a SIM card, and a communication device,such as a communication interface for an IC card, that can perform bothwireless communication and wired communication, with a simpleconfiguration of the devices by minimizing the number of lines forconnecting the devices.

According to an embodiment of the present disclosure, there is provideda communication system including a wired communication device thatperforms wired communication, and a communication device that cancommunicate with both a wireless communication device that performswireless communication and the wired communication device. Thecommunication device includes a clock output unit operable to output aclock to be supplied to the wired communication device, and a modulatoroperable to perform amplitude shift keying (ASK) modulation on the clockby using a signal corresponding to data to be sent to the wiredcommunication device as a modulation subject signal and to output aresulting modulated signal. The wired communication device includes aclock extracting unit operable to extract the clock from the modulatedsignal, a signal extracting unit operable to extract the modulationsubject signal from the modulated signal, and a processing unit operableto process the modulation subject signal extracted by the signalextracting unit in accordance with the clock extracted by the clockextracting unit and also to output a signal corresponding to data to besent to the communication device. The communication device and the wiredcommunication device are connected to each other by a first connectingline through which the modulated signal output from the modulator issent from the communication device to the wired communication device,and a second connecting line, which is different from the firstconnecting line, through which the signal output from the processingunit is sent from the wired communication device to the communicationdevice.

The system is a logical set of a plurality of devices, and it is notnecessary that the devices be located in the same housing.

According to another embodiment of the present disclosure, there isprovided a communication device that can communicate with both awireless communication device that performs wireless communication and awired communication device that performs wired communication. Thecommunication device includes a clock output unit operable to output aclock to be supplied to the wired communication device, and a modulatoroperable to perform ASK modulation on the clock by using a signalcorresponding to data to be sent to the wired communication device as amodulation subject signal and to output a resulting modulated signal.The communication device is connected to the wired communication deviceby a first connecting line through which the modulated signal outputfrom the modulator is sent from the communication device to the wiredcommunication device, and a second connecting line, which is differentfrom the first connecting line, through which a signal corresponding todata to be sent from the wired communication device to the communicationdevice is sent from the wired communication device to the communicationdevice.

According to another embodiment of the present disclosure, there isprovided a first communication method for a communication device thatcan communicate with both a wireless communication device that performswireless communication and a wired communication device that performswired communication. The first communication method includes the stepsof performing ASK modulation on a clock by a modulation subject signalto output a resulting modulated signal by using a modulator, sending themodulated signal to the wired communication device through a firstconnecting line through which the modulated signal output from themodulator is sent from the communication device to the wiredcommunication device, and receiving the signal sent from the wiredcommunication device through a second connecting line, which isdifferent from the first connecting line, through which a signalcorresponding to data to be sent from the wired communication device tothe communication device is sent from the wired communication device tothe communication device.

According to another embodiment of the present disclosure, there isprovided a wired communication device that performs wired communicationwith a communication device that can communicate with both a wirelesscommunication device that performs wireless communication and the wiredcommunication device. The wired communication device includes a clockextracting unit operable to extract a clock from a modulated signalwhich is obtained by performing ASK modulation on the clock by using asignal corresponding to data as a modulation subject signal and which issent from the communication device, a signal extracting unit operable toextract the modulation subject signal from the modulated signal, and aprocessing unit operable to process the modulation subject signalextracted by the signal extracting unit in accordance with the clockextracted by the clock extracting unit and also to output a signalcorresponding to data to be sent to the communication device. The wiredcommunication device is connected to the communication device by a firstconnecting line through which the modulated signal output from thecommunication device is sent from the communication device to the wiredcommunication device and a second connecting line, which is differentfrom the first connecting line, through which the signal output from theprocessing unit is sent from the wired communication device to thecommunication device.

According to another embodiment of the present disclosure, there isprovided a second communication method for a wired communication devicethat performs wired communication with a communication device that cancommunicate with both a wireless communication device that performswireless communication and the wired communication device. The secondcommunication method includes the steps of receiving a modulated signalfrom the communication device by the wired communication device througha first connecting line through which the modulated signal output fromthe communication device is sent, extracting the clock from themodulated signal by a clock extracting unit and extracting themodulation subject signal from the modulated signal by a signalextracting unit, and sending the signal output from a processing unitfrom the wired communication device to the communication device througha second connecting line, which is different from the first connectingline, through which the signal output from the processor is sent.

Accordingly, in an embodiment of the present disclosure, a modulatedsignal obtained by performing ASK modulation on a clock by a modulationsubject signal is sent from the communication device to the wiredcommunication device through the first connecting line, and a signaloutput from the processor is sent from the wired communication device tothe communication device through the second connecting line.

According to an embodiment of the present disclosure, wiredcommunication can be performed with a simple device configuration byminimizing the number of lines connecting the devices.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram illustrating an example of the configurationof a communication system according to an embodiment of the presentdisclosure.

FIG. 2 illustrates sending and receiving of data between a messageprocessor and a wireless communication device.

FIG. 3 illustrates sending and receiving of data between a controllerand the message processor.

FIG. 4 is a block diagram illustrating an example of configuration of anNFC interface and the message processor.

FIG. 5 is a block diagram illustrating an example of the configurationof a modulator of the NFC interface.

FIG. 6 is a waveform diagram illustrating a modulation subject signalsupplied to the modulator and a SIGOUT signal output from the modulator.

FIG. 7 schematically illustrates the modulation subject signal and theSIGOUT signal (modulated signal).

FIG. 8 is a block diagram illustrating an example of the configurationof a clock extracting unit and a signal extracting unit.

FIG. 9 is a waveform diagram illustrating a SIGIN signal.

FIG. 10 illustrates wired communication between the NFC interface andthe message processor.

DETAILED DESCRIPTION

The communication system according to an embodiment of the presentdisclosure includes a wired communication device (for example, a messageprocessor 14 shown in FIG. 1) that performs wired communication and acommunication device (an NFC interface 12 shown in FIG. 1) that iscapable of communicating with both a wireless communication device (forexample, a wireless communication device 2 shown in FIG. 1) thatperforms wireless communication and the wired communication device. Thecommunication device includes a clock output unit (for example, a clockselector 46 shown in FIG. 4) operable to output a clock to be suppliedto the wired communication device, and a modulator (for example, amodulator 47 shown in FIG. 4) operable to perform ASK modulation on theclock by using a signal corresponding to data to be sent to the wiredcommunication device as a modulation subject signal and to output aresulting modulated signal. The wired communication device including aclock extracting unit (for example, a clock extracting unit 52 shown inFIG. 4) operable to extract the clock from the modulated signal, asignal extracting unit (for example, a signal extracting unit 53 shownin FIG. 4) operable to extract the modulation subject signal from themodulated signal, and a processing unit (a processing unit shown in FIG.54 shown in FIG. 4) operable to process the modulation subject signalextracted by the signal extracting unit in accordance with the clockextracted by the clock extracting unit and also to output a signalcorresponding to data to be sent to the communication device. Thecommunication device and the wired communication device are connected toeach other by a first connecting line (for example, a SIGOUT line shownin FIG. 1) through which the modulated signal output from the modulatoris sent from the communication device to the wired communication deviceand a second connecting line (for example, a SIGIN line shown in FIG.1), which is different from the first connecting line, through which thesignal output from the processing unit is sent from the wiredcommunication device to the communication device.

The communication device (for example, the NFC interface 12 shown inFIG. 1) according to an embodiment of the present disclosure cancommunicate with both a wireless communication device (for example, thewireless communication device 2 shown in FIG. 1) that performs wirelesscommunication and a wired communication device (for example, the messageprocessor 14 shown in FIG. 1) that performs wired communication. Thecommunication device includes a clock output unit (for example, theclock selector 46 shown in FIG. 4) operable to output a clock to besupplied to the wired communication device, and a modulator (forexample, the modulator 47 shown in FIG. 4) operable to perform ASKmodulation on the clock by using a signal corresponding to data to besent to the wired communication device as a modulation subject signaland to output a resulting modulated signal. The communication device isconnected to the wired communication device by a first connecting line(for example, the SIGOUT line shown in FIG. 1) through which themodulated signal output from the modulator is sent from thecommunication device to the wired communication device, and a secondconnecting line (for example, the SIGIN line shown in FIG. 1), which isdifferent from the first connecting line, through which a signalcorresponding to data to be sent from the wired communication device tothe communication device is sent from the wired communication device tothe communication device.

The first communication method according to an embodiment of the presentdisclosure is used for a communication device (for example, the NFCinterface 12 shown in FIG. 1) that can communicate with both a wirelesscommunication device (for example, the wireless communication device 2shown in FIG. 1) that performs wireless communication and a wiredcommunication device (for example, the message processor 14 shown inFIG. 1) that performs wired communication. The communication deviceincludes a clock output unit (for example, the clock selector 46 shownin FIG. 4) operable to output a clock to be supplied to the wiredcommunication device, and a modulator (for example, the modulator 47shown in FIG. 4) operable to perform ASK modulation on the clock byusing a signal corresponding to data to be sent to the wiredcommunication device as a modulation subject signal and to output amodulated signal. The first communication method includes the steps ofperforming ASK modulation on the clock by the modulation subject signalto output the modulated signal by using the modulator, sending themodulated signal to the wired communication device through a firstconnecting line (for example, the SIGOUT line shown in FIG. 1) throughwhich the modulated signal output from the modulator is sent from thecommunication device to the wired communication device, and receivingthe signal sent from the wired communication device through a secondconnecting line (for example, the SIGIN line shown in FIG. 1), which isdifferent from the first connecting line, through which a signalcorresponding to data to be sent from the wired communication device tothe communication device is sent from the wired communication device tothe communication device.

The wired communication device (for example, the message processor 14shown in FIG. 1) according to an embodiment of the present disclosureperforms wired communication with a communication device (for example,the NFC interface 12 shown in FIG. 1) that can communicate with both awireless communication device (for example, the wireless communicationdevice 2 shown in FIG. 1) that performs wireless communication and thewired communication device. The wired communication device includes aclock extracting unit (the clock extracting unit 52 shown in FIG. 4)operable to extract a clock from a modulated signal which is obtained byperforming ASK modulation on the clock by using a signal correspondingto data as a modulation subject signal and which is sent from thecommunication device, a signal extracting unit (for example, the signalextracting unit 53 shown in FIG. 4) operable to extract the modulationsubject signal from the modulated signal, and a processing unit (forexample, the processing unit 54 shown in FIG. 4) operable to process themodulation subject signal extracted by the signal extracting unit inaccordance with the clock extracted by the clock extracting unit andalso to output a signal corresponding to data to be sent to thecommunication device. The wired communication device is connected to thecommunication device by a first connecting line (for example, the SIGOUTline shown in FIG. 1) through which the modulated signal output from thecommunication device is sent from the communication device to the wiredcommunication device, and a second connecting line (the SIGIN signalshown in FIG. 1), which is different from the first connecting line,through which the signal output from the processing unit is sent fromthe wired communication device to the communication device.

The second communication method according to an embodiment of thepresent disclosure is used for a wired communication device (forexample, the message processor 14 shown in FIG. 1) that performs wiredcommunication with a communication device (for example, the NFCinterface 12 shown in FIG. 1) that can communicate with both a wirelesscommunication device (for example, the wireless communication device 2shown in FIG. 1) that performs wireless communication and the wiredcommunication device. The wired communication device includes a clockextracting unit (for example, the clock extracting unit 52 shown in FIG.4) operable to extract a clock from a modulated signal which is obtainedby performing ASK modulation on the clock by using a signalcorresponding to data as a modulation subject signal and which is sentfrom the communication device, a signal extracting unit (for example,the signal extracting unit 53 shown in FIG. 4) operable to extract themodulation subject signal from the modulated signal, and a processingunit (for example, the processing unit 54 shown in FIG. 4) operable toprocess the modulation subject signal extracted by the signal extractingunit in accordance with the clock extracted by the clock extracting unitand also to output a signal corresponding to data to be sent to thecommunication device. The second communication method includes the stepsof receiving the modulated signal from the communication device by thewired communication device through a first connecting line (for example,the SIGOUT line shown in FIG. 1) through which the modulated signaloutput from the communication device is sent, extracting the clock fromthe modulated signal by the clock extracting unit and extracting themodulation subject signal from the modulated signal by the signalextracting unit, and sending the signal output from the processing unitfrom the wired communication device to the communication device througha second connecting line (for example, the SIGIN line shown in FIG. 1),which is different from the first connecting line, through which thesignal output from the processor is sent.

An embodiment of the present disclosure is described below withreference to the accompanying drawings.

FIG. 1 illustrates the configuration of a communication system accordingto an embodiment of the present disclosure.

The communication system includes a cellular telephone 1 and a wirelesscommunication device 2 between which wireless communication can beperformed.

That is, both the cellular telephone 1 and the wireless communicationdevice 2 are configured as devices that perform near field communicationin conformity with NFCIP-1 as wireless communication (hereinafter suchdevices are sometimes referred to as “NFC devices”).

NFC devices can perform near field communication (NFC) based onelectromagnetic induction with other NFC devices by using a carrier wavehaving a single frequency, such as 13.56 MHz in the IndustrialScientific Medical (ISM) band.

Near field communication is communication that can be performed betweendevices located away from each other at a distance within several tensof centimeters, and includes communication that is performed betweendevices (or casings accommodating the devices therein) in contact witheach other.

NFC devices can perform near field communication in two communicationmodes, i.e., the passive mode and the active mode, as stated above. Itis now assumed that two NFC devices (first and second NFC devices) arecommunicating with each other. In the passive mode, the first NFC devicegenerates electromagnetic waves and modulates a carrier wavecorresponding to the electromagnetic waves to send data to the secondNFC device. The second NFC device receives the carrier wave from thefirst NFC device and performs load modulation on it to send data to thefirst NFC device.

In the active mode, the two NFC devices each generate electromagneticwaves and modulate a carrier wave corresponding to the electromagneticwaves to send data.

In near field communication based on electromagnetic induction, an NFCdevice that starts communication by first outputting electromagneticwaves, i.e., an NFC device that takes the initiative in communication,is referred to as an “initiator”. In near field communication, theinitiator sends a command to the other communicating device, and thecommunicating device returns a response to the command to the initiator.The communicating device that returns a response is referred to as a“target”.

If one of the two NFC devices outputs electromagnetic waves to startcommunication with the other NFC device, the first NFC device is theinitiator, and the other NFC device is the target.

In the passive mode, the initiator continues outputting electromagneticwaves and modulates them to send data to the target. The target receivesthe electromagnetic waves from the initiator and performs loadmodulation on them to send data to the initiator.

In the active mode, the initiator starts to output electromagnetic wavesand modulates them to send data to the target. Upon finishing sendingthe data, the initiator stops outputting electromagnetic waves. Then,the target starts to output electromagnetic waves and modulates them tosend data to the initiator. Upon finishing sending the data, the targetstops outputting electromagnetic waves.

An NFC device can become the initiator by first outputtingelectromagnetic waves to start communication. In the active mode, theNFC device outputs electromagnetic waves by itself regardless of whetherit is the initiator or the target. Accordingly, it is possible that aplurality of NFC devices simultaneously output electromagnetic waves, inwhich case, if such NFC devices are located close to each other, acollision occurs and communication is discontinued.

Accordingly, an NFC device checks for a radio frequency (RF) fieldformed by electromagnetic waves generated from other devices (such asNFC devices), and only when there is no electromagnetic waves from theother devices, the NFC device starts to output electromagnetic waves,thereby avoiding the occurrence of collision. This processing isreferred to as RF collision avoidance (RFCA) processing.

In RFCA processing, an NFC device starts to output electromagnetic wavesif electromagnetic waves from other devices are not detected for apredetermined continuous period of time, which is determined by usingrandom numbers. This reduces the possibility of a plurality of NFCdevices starting outputting electromagnetic waves at the same time.

NFC devices can send data at various transmission rates, such as 106kilo bit per second (kbps), 212 kbps, and 424 kbps, and can also changethe transmission rate while performing communication which is started atanother transmission rate.

The cellular telephone 1 and the wireless communication device 2configured as described above include NFC interfaces 12 and 22,respectively, which serve as interfaces for performing communication inconformity with NFCIP-1.

More specifically, the cellular telephone 1 includes an antenna 11, theNFC interface 12, a controller 13, and a message processor 14.

The antenna 11 forms a closed loop coil, and when a current flowing inthe coil is changed, electromagnetic waves are output from the antenna11. When electromagnetic waves (magnetic fluxes) flowing in the coil,which serves as the antenna 11, are changed, a current flows in theantenna 11. A signal (current) flowing in the antenna 11 is supplied tothe NFC interface 12.

The NFC interface 12 is, for example, a one-chip IC, which performscommunication in conformity with NFCIP-1, and performs near fieldcommunication (wireless communication) with the wireless communicationdevice 2 or another NFC device via the antenna 11.

The NFC interface 12 also serves as an interface that performs wiredcommunication, and is connected to the message processor 14 thatperforms wired communication by a SIGOUT line (first connecting line), aSIGIN line (second connecting line), and a GND line.

The SIGOUT line is an electrical wire through which a SIGOUT signal,which is described below, is sent from the NFC interface 12 to themessage processor 14. The SIGIN line is an electrical wire differentfrom the SIGOUT line, through which a SIGIN signal, which is describedbelow, is sent from the message processor 14 to the NFC interface 12.The GND line is grounded.

The NFC interface 12 sends data (including commands) to the messageprocessor 14 through the SIGOUT line, and receives data from the messageprocessor 14 through the SIGIN line, thereby performing wiredcommunication with the message processor 14.

The NFC interface 12 and the message processor 14 each have terminals tobe connected to the SIGOUT line, SIGIN line, and GND line. However, suchterminals are not shown for simple representation.

The NFC interface 12 also includes an interface for performingcommunication (wired communication) with the controller 13 to send andreceive various data to and from the controller 13.

The controller 13 controls blocks (not shown) that serve as a cellulartelephone unit of the cellular telephone 1. The blocks serving as acellular telephone include a block having a calling function and a blockhaving a web-browsing and e-mail-forming function.

The message processor 14 processes messages, and more specifically, themessage processor 14 performs wired communication (sending and receivingdata by using wired means) to receive data, and stores it if necessary.The message processor 14 also reads stored data and sends it by wiredcommunication.

The message processor 14 is connected to the NFC interface 12 throughthe three connecting lines, i.e., the SIGOUT line, SIGIN line, and GNDline. The message processor 14 sends data to the NFC interface 12through the SIGIN line and receives data from the NFC interface 12through the SIGOUT line, thereby performing wired communication with theNFC interface 12.

The message processor 14 may be integrated in the cellular telephone 1.Alternatively, the message processor 14 may be hardware that can easilybe installed or removed into or from the cellular telephone 1 by a user,in which case, when the message processor 14 is installed in thecellular telephone 1, the terminals (not shown) of the message processor14 are electrically connected to the SIGOUT line, SIGIN line, and GNDline.

The message processor 14 can be formed as a SIM card or a UIM card. Inthis case, the message processor 14 may have a built-in tamper-resistantsecure application module (SAM) that manages e-money or keys used forauthentication or encryption of data. In the message processor 14 havinga built-in SAM, a portion serving as the SIM card or the UIM card and aportion serving as the SAM may be integrated into a one-chip IC or maybe formed as different one-chip ICs.

In the cellular telephone 1 shown in FIG. 1, in addition to the SIGOUTline, SIGIN line, and GND line, a line for supplying power Vcc isconnected to the message processor 14, and power Vcc is supplied to themessage processor 14 via the power supply line to operate the messageprocessor 14. There is also another line, which is different from theSIGOUT line, SIGIN line, and GND line, for connecting the messageprocessor 14 to the NFC interface 12, and power can be supplied from theNFC interface 12 to the message processor 14 through that line.

The wireless communication device 2 includes an antenna 21, the NFCinterface 22, and a controller 23. The antenna 21 and the NFC interface22 are configured similarly to the antenna 11 and the NFC interface 12,respectively, of the cellular telephone 1.

Since the wireless communication device 2 is not provided with a blockcorresponding to the message processor 14, the NFC interface 22 may beprovided with or without a function serving as an interface thatperforms wired communication with a block corresponding to the messageprocessor 14.

The controller 23 executes various types of processing. Morespecifically, if the wireless communication device 2 is a reader/writerof an automatic ticketing machine, the controller 23 controls the NFCinterface 22 to read information (such as the expire date and thetraveling zone) from an IC card, which serves as a commuter pass, bynear field communication when the IC card is located close to thewireless communication device 2, and then checks whether the informationconcerning the commuter pass is appropriate. If the wirelesscommunication device 2 is an IC card that can conduct electronicsettlement, the controller 23 updates the balance of e-money in responseto a NFC device (not shown) that stores e-money and requests thecontroller 23 to conduct electronic settlement.

The wireless communication device 2 may be formed as a reader/writer anda personal computer (PC). In this case, the PC runs an application(program) to implement the controller 23.

The cellular telephone 1 and the wireless communication device 2configured as described above are both NFC devices so that they canperform near field communication in conformity with NFCIP-1.

That is, the NFC interface 12 of the cellular telephone 1 can performnear field communication with the NFC interface 22 of the wirelesscommunication device 2 in conformity with NFCIP-1.

The NFC interface 12 of the cellular telephone 1 can also perform wiredcommunication with the message processor 14 by being connected theretothrough the SIGOUT line, SIGIN line, and GND line. The NFC interface 12can also perform wired communication (controller communication) with thecontroller 13.

Thus, according to the communication system shown in FIG. 1, the NFCinterface 12 of the cellular telephone 1 can receive data from the NFCinterface 22 of the wireless communication device 2 and further sendsthe data to the message processor 14 through the SIGOUT line by wiredcommunication. The NFC interface 12 can also receive data (for example,data output from the message processor 14 as a response to data sentfrom the wireless communication device 2 via the NFC interface 12) fromthe message processor 14 through the SIGIN line by wired communicationand further transfers the data to the wireless communication device 2 bywireless communication.

As a result, the message processor 14 and the wireless communicationdevice 2 can send and receive data, as shown in FIG. 2, with each othervia the NFC interface 12. Accordingly, if the message processor 14stores e-money and the wireless communication device 2 conductselectronic settlement, the wireless communication device 2 reads e-moneystored in the message processor 14 via the NFC interface 12 to conductelectronic settlement on a product purchased by the user of the cellulartelephone 1.

In the communication system shown in FIG. 1, the NFC interface 12 of thecellular telephone 1 can receive data from the controller 13 and furthertransfers the data to the message processor 14 through the SIGOUT lineby wired communication. The NFC interface 12 can also receive data fromthe message processor 14 through the SIGIN line by wired communicationand further transfers the data to the controller 13.

As a result, the controller 13 and the message processor 14 can send andreceive data, as shown in FIG. 3, via the NFC interface 12. Accordingly,if the message processor 14 stores e-money, the controller 13 can readthe outstanding balance of e-money from the message processor 14 via theNFC interface 12 and displays the balance on a display unit (not shown)of the cellular telephone 1, thereby allowing the user of the cellulartelephone 1 to check the balance of e-money.

In the communication system 1, the controller 13 and the wirelesscommunication device 2 can also send and receive data with each othervia the NFC interface 12 in a manner similar to sending and receiving ofdata between the message processor 14 and the wireless communicationdevice 2 via the NFC interface 12 as shown in FIG. 2 or between thecontroller 13 and the message processor 14 via the NFC interface 12 asshown in FIG. 3.

Thus, if the wireless communication device 2 is an IC card storinge-money, the controller 13 reads the balance of e-money stored in thewireless communication device 2 via the NFC interface 12 and displaysthe balance on a display unit (not shown) of the cellular telephone 1,thereby allowing the user to check the balance of e-money stored in(charged to) the wireless communication device 2 by using the cellulartelephone 1.

FIG. 4 illustrates an example of the configuration of the NFC interface12 and the message processor 14 shown in FIG. 1. In FIG. 4, among theSIGOUT line, SIGIN line, and GND line for connecting the NFC interface12 and the message processor 14, the GND line is not shown.

In the NFC interface 12, a demodulate processor 41 is connected to theantenna 11 to detect a current flowing in the antenna 11, and furtherdetects the RF field formed by electromagnetic waves generated byanother device. The demodulate processor 41 also tunes the currentflowing in the antenna 11 and extracts an information signal to amplifythe resulting signal by conducting, for example, amplitude shift keying(ASK) demodulation. As a result, the signal can be demodulated. Thedemodulate processor 41 then supplies the demodulated signal, forexample, Manchester codes (signal corresponding to data), to a serialdata switch 42.

The demodulate processor 41 also generates a clock (clock signal)(external clock) having a frequency of 13.56 MHz, which is a carrierfrequency, adopted in NFCIP-1 by tuning the current flowing in theantenna 11 and extracting an information signal, and supplies thegenerated clock to a clock selector 46.

The serial data switch 42 supplies the Manchester codes received fromthe demodulate processor 41 to a data processor 43 or a modulator 47.The serial data switch 42 also supplies Manchester codes received fromthe data processor 43 to a modulator 44 or the modulator 47. The serialdata switch 42 also supplies Manchester codes received from the messageprocessor 14 through the SIGIN line as a SIGIN signal to the dataprocessor 43 or the modulator 44.

The data processor 43 codes data by using a predetermined coding methodand also decodes data coded with a predetermined coding method. Morespecifically, the data processor 43 codes data supplied from thecontroller 13 via a central processing unit (CPU) 48 into Manchestercodes and supplies the Manchester codes to the serial data switch 42.The data processor 43 also decodes Manchester codes supplied from theserial data switch 42 and supplies the resulting data to the controller13 via the CPU 48.

Although in the data processor 43 Manchester coding/decoding is used,another type of coding/decoding, for example, modified Millercoding/decoding or non-return-to-zero (NRZ) coding/decoding, may beemployed.

In the passive mode, the modulator 44 changes the impedance when anexternal source views the coil, which serves as the antenna 11, inaccordance with the signal (for example, Manchester codes) supplied fromthe serial data switch 42. In this case, if an RF field (magnetic field)is formed around the antenna 11 by electromagnetic waves output fromanother device (for example, the wireless communication device 2 shownin FIG. 1) as a carrier wave, the RF field is changed in response to achange in the impedance. Then, the carrier wave as electromagnetic wavesoutput from the wireless communication device 2 is modulated(load-modulated) in accordance with the signal supplied from the serialdata switch 42, and then, the signal (Manchester codes) from the serialdata switch 42 is sent to the wireless communication device 2 thatcontinues outputting electromagnetic waves.

In the active mode, the modulator 44 generates electromagnetic waves asa carrier wave by allowing a current to flow in the antenna 11, and thenmodulates the carrier wave by the signal supplied from the serial dataswitch 42 to output the electromagnetic waves as a modulated signal.

As the modulation method used in the modulator 44, ASK modulation may beemployed. However, the modulation method is not restricted to ASKmodulation, and another modulation, for example, phase shift keying(PSK) modulation or quadrature amplitude modulation (QAM), may beemployed. In NFCIP-1, the modulation factor of ASK modulation is 8% to30%.

A clock generator 45 integrates a quarts oscillator or a ceramicoscillator therein, and generates a clock (internal clock) having afrequency similar to that of the carrier wave employed in NFCIP-1 tosupply the clock to the clock selector 46.

The clock selector 46 selects one of the external clock supplied fromthe demodulate processor 41 and the internal clock supplied from theclock generator 45, and outputs the selected clock to the modulator 47and the necessary blocks of the NFC interface 12.

More specifically, when an external clock is supplied from thedemodulate processor 41, that is, when an NFC device, such as thewireless communication device 2, is located near the NFC interface 12(cellular telephone 1) and an RF field is formed by the presence of theNFC device, the clock selector 46 selects the external clock suppliedfrom the demodulate processor 41. On the other hand, when an externalclock is not supplied from the demodulate processor 41, that is, when anRF field is not formed since an NFC device, such as the wirelesscommunication device 2, is not located near the NFC interface 12, theclock selector 46 selects the internal clock supplied from the clockgenerator 45.

The modulator 47 performs ASK modulation on the clock output from theclock selector 46 by using Manchester codes supplied from the serialdata switch 42, that is, a signal corresponding to data to be sent fromthe serial data switch 42 to the message processor 14, as a signal to bemodulated (hereinafter referred to as a “a modulation subject signal”),and outputs the resulting modulated signal to the SIGOUT line as aSIGOUT signal.

The CPU 48 performs processing on the data if necessary to output theprocessed data to the data processor 43 or the controller 13. It is notessential that the NFC interface 12 be provided with the CPU 48.

The message processor 14 includes a signal processor 51. The signalprocessor 51 includes a clock extracting unit 52, a signal extractingunit 53, and a processing unit 54.

The clock extracting unit 52 extracts the clock from the modulatedsignal (SIGOUT signal) sent from the modulator 47 via the SIGOUT lineand supplies the extracted clock to the processing unit 54 and necessaryblocks of the message processor 14.

The signal extracting unit 53 extracts the modulation subject signal(Manchester codes) from the modulated signal (SIGOUT signal) sent fromthe modulator 47 via the SIGOUT line and supplies the extractedmodulation subject signal to the processing unit 54.

The processing unit 54 decodes the Manchester codes supplied from thesignal extracting unit 53 in accordance with the clock (insynchronization with the clock) extracted by the clock extracting unit52, and stores the decoded data. The processing unit 54 also codes thestored data into Manchester codes in accordance with the clock extractedby the clock extracting unit 52, and outputs the coded data to the SIGINline as a SIGIN signal to be sent to the NFC interface 12. Then, theSIGIN signal is sent from the message processor 14 to the NFC interface12 through the SIGIN line.

In operation, the NFC interface 12 may receive power from batteries (notshown) of the cellular telephone 1 (FIG. 1). Alternatively, the NFCinterface 12 may obtain power by using the demodulate processor 41 byrectifying a current flowing in the antenna 11 by an RF field formed byan NFC device, such as the wireless communication device 2, located nearthe NFC interface 12.

Alternatively, the NFC interface 12 may be operated by a combination ofbatteries of the cellular telephone 1 and a current flowing in theantenna 11 by the presence of an NFC device. More specifically, if theremaining capacity of batteries of the cellular telephone 1 is greaterthan or equal to a predetermined threshold, the NFC interface 12 may beoperated by the batteries. If the remaining capacity of the batteries issmaller than the threshold, the NFC interface 12 may be operated byusing power obtained from a current flowing in the antenna 11 by theformation of an RF field.

In the NFC interface 12 and the message processor 14 configured asdescribed above, when sending data from the NFC interface 12 to themessage processor 14, the modulator 47 of the NFC interface 12 modulatesthe clock output from the clock selector 46 by using Manchester codes tobe sent to the message processor 14 as a modulation subject signal, andsends the resulting modulated signal to the message processor 14 as theSIGOUT signal through the SIGOUT line.

n the message processor 14, the signal processor 51 receives the SIGOUTsignal through the SIGOUT line and supplies the SIGOUT signal to theclock extracting unit 52 and the signal extracting unit 53. The clockextracting unit 52 extracts the clock from the SIGOUT signal andsupplies the extracted clock to the processing unit 54. The signalextracting unit 53 extracts the Manchester codes from the SIGOUT signalas the modulation subject signal and supplies the extracted Manchestercodes to the processing unit 54. The processing unit 54 processes theManchester codes supplied from the signal extracting unit 53 insynchronization with the clock supplied from the clock extracting unit52, and more specifically, the processing unit 54 decodes the Manchestercodes and stores them if necessary.

When sending data from the message processor 14 to the NFC interface 12,the modulator 47 of the NFC interface 12 sends the SIGOUT signalgenerated by modulating the clock output from the clock selector 46 byusing the output from the serial data switch 42 to the message processor14 through the SIGOUT line. In this case, if data (Manchester codes) isnot output from the serial data switch 42, the modulator 47 sends theclock itself from the clock selector 46 to the message processor 14. Inthe message processor 14, the clock extracting unit 52 extracts theclock from the SIGOUT signal and supplies the extracted clock to theprocessing unit 54.

The processing unit 54 outputs Manchester codes to be sent to the NFCinterface 12 to the SIGIN line as the SIGIN signal in synchronizationwith the clock output from the clock extracting unit 52.

More specifically, the processing unit 54 reads data to be sent to theNFC interface 12, and codes the data into Manchester codes if they havenot been coded. The processing unit 54 then outputs the Manchester codesto the SIGIN line as the SIGIN signal. Then, the data can be sent fromthe message processor 14 to the NFC interface 12 through the SIGIN line.

In the NFC interface 12, the serial data switch 42 receives the SIGINsignal (Manchester codes) sent from the message processor 14 asdescribed above.

FIG. 5 illustrates an example of the configuration of the modulator 47shown in FIG. 4.

As discussed above, the modulator 47 receives Manchester codes as asignal to be sent from the serial data switch 42 to the messageprocessor 14 and the clock output from the clock selector 46.

The modulator 47 includes an amplifier 61. The amplifier 61 amplifiesthe clock output from the clock selector 46 in accordance with theManchester codes (signal) supplied from the serial data switch 42 toperform ASK modulation on the clock by using the Manchester codes as themodulation subject signal. The amplifier 61 then outputs theASK-modulated signal to the SIGOUT line as the SIGOUT signal.

In the modulator 47, the ASK modulation factor is 8% to 30%, which isadopted in NFCIP-1 as the modulation factor of carrier ASK modulation.However, the modulation factor is not restricted to 8% to 30%, and maybe any value that allows the clock extracting unit 52 of the messageprocessor 14 to extract the clock with high precision.

FIG. 6 illustrates an example of the modulation subject signal suppliedto the amplifier 61 of the modulator 47 shown in FIG. 5 and an exampleof the modulated signal output from the modulator 47 as the SIGOUTsignal. In FIG. 6, the horizontal axis represents the time, and thevertical axis designates the amplitude. The same applies to FIGS. 7 and9.

The first section from the top in FIG. 6 illustrates an example of themodulation subject signal. The modulation subject signal is Manchestercodes, and more precisely, a signal corresponding to data (bits) beforebeing coded into Manchester codes. More specifically, when the dataindicates 0 (binary), the Manchester code change from the low (L) levelto the high (H) level. When the data indicates 1 (binary), theManchester codes change from the H level to the L level.

The second section from the top in FIG. 6 illustrates an example of themodulated signal (SIGOUT signal) generated by modulating a pulse trainas the clock by using the modulation subject signal indicated in thefirst section in FIG. 6.

When the modulation subject signal is at the H level, the amplifier 61of the modulator 47 amplifies the clock by a factor of 1, and when themodulation subject signal is at the L level, the amplifier 61 amplifiesthe clock by a factor greater than 0 and smaller than 1 (for example,the factor from 0.92 to 0.7).

The third section from the top in FIG. 6 illustrates a waveform of acurrent (modulated signal) flowing in the antenna 11 when the modulator44 modulates a sine wave as a carrier by the modulation subject signalindicated in the first section in FIG. 6.

As discussed above, the modulator 44 performs ASK modulation on thecarrier by using the Manchester codes obtained by coding the data. Inboth the modulators 44 and 47, the modulation subject signal is theManchester codes, and the modulation method is ASK modulation.Accordingly, the current (modulated signal) flowing in the antenna 11generated by performing modulation by the modulator 44 is similar to theSIGOUT signal (modulated signal) obtained by performing modulation bythe modulator 47, except that the types of signals modulated by themodulation subject signal are different, i.e., the carrier and theclock.

If the frequency of the clock output from the clock selector 46 (FIG. 4)is 13.56 MHz and if the transmission rate of the Manchester codessupplied from the serial data switch 42 to the modulator 47 is 212 kbps,there are about 64 pulses in one symbol (one bit) of the data (≈13.56MHz/212 kbps).

FIG. 7 is an enlarged view illustrating part of the modulation subjectsignal and the SIGOUT signal (modulated signal) shown in FIG. 6.

The first section from the top in FIG. 7 illustrates the clock suppliedfrom the clock selector 46 to the modulator 47. The second section fromthe top in FIG. 7 illustrates the modulation subject signal (Manchestercodes) supplied from the serial data switch 42 to the modulator 47. Thethird section from the top in FIG. 7 illustrates the SIGOUT signal(modulated signal) obtained by performing ASK modulation on the clockindicated in the first section by the modulation subject signalindicated in the second section.

It is now assumed that the minimum voltage and the maximum voltage ofthe clock pulses shown in the first section is 0 V and Vc V,respectively. In this case, when the modulation subject signal is at theH level, the voltage of the SIGOUT signal is Vc V, as indicated in thethird section. When the modulation subject signal is at the L level, thevoltage of the SIGOUT signal is Vc′ V, which is larger than 0 V andsmaller than Vc V, as indicated in the third section.

FIG. 7 shows that, after ASK modulation is conducted on the clock by themodulation subject signal, the rising edges and the falling edges of theclock of the resulting SIGOUT signal can be maintained although thelevels thereof are different from those of the clock.

FIG. 8 illustrates an example of the configuration of the clockextracting unit 52 and the signal extracting unit 53 shown in FIG. 4.

The clock extracting unit 52 includes a comparison voltage output unit71 and a comparator 72.

The comparison voltage output unit 71 outputs a predetermined thresholdTH1, which is a voltage to be compared with the SIGOUT signal suppliedfrom the NFC interface 12 through the SIGOUT line, to the comparator 72

In this case, if the voltage of the SIGOUT signal takes three values,such as 0, Vc′, and Vc, as indicated in the third part in FIG. 7, thepredetermined threshold TH1 is greater than 0 and smaller than Vc′, forexample, Vc′/2.

The comparator 72 compares the SIGOUT signal supplied from the NFCinterface 12 through the SIGOUT line with the threshold TH1 suppliedfrom the comparison voltage output unit 71 to extract and output theclock from the SIGOUT signal.

More specifically, upon comparing the SIGOUT signal with the thresholdTH1, if the SIGOUT signal is greater than or equal to the threshold TH1,the comparator 72 outputs the H level, and if the SIGOUT signal issmaller than the threshold TH1, the comparator 72 outputs the L level,thereby extracting the clock indicated in the first part in FIG. 7 fromthe SIGOUT signal indicated in the third part in FIG. 7.

As stated above, since, in the SIGOUT signal, the rising edges and thefalling edges of the clock can be maintained, the clock can be obtainedeasily and precisely only by comparing the SIGOUT signal with thethreshold TH1.

The signal extracting unit 53 includes an envelope detector 81, acomparison voltage output unit 82, and a comparator 83.

The envelope detector 81 detects the envelope of the SIGOUT signalsupplied from the NFC interface 12 through the SIGOUT line and suppliesthe resulting envelope signal to the comparator 83.

The comparison voltage output unit 82 outputs a predetermined thresholdTH2, which is a voltage to be compared with the envelope signal suppliedfrom the envelope detector 81, to the comparator 83.

In this case, if the voltage of the SIGOUT signal takes three values,such as 0, Vc′, and Vc, as indicated in the third part in FIG. 7, thepredetermined threshold TH2 is greater than Vc′ and smaller than Vc, forexample, the average of Vc′ and Vc.

The comparator 83 compares the envelope signal supplied from theenvelope detector 81 with the threshold TH2 supplied from the comparisonvoltage output unit 82 to extract and output the modulation subjectsignal from the SIGOUT signal.

More specifically, upon comparing the envelope signal with the thresholdTH2, if the envelope signal is greater than or equal to the thresholdTH2, the comparator 83 outputs the H level, and if the envelope signalis smaller than the threshold TH2, the comparator 83 outputs the Llevel, thereby extracting the modulation subject signal indicated in thesecond part in FIG. 7 from the envelope signal of the SIGOUT signalindicated in the third part in FIG. 7.

The SIGOUT signal is a modulated signal generated by modulating theclock by the modulation subject signal, as stated above. Accordingly, byobtaining and comparing the envelope of the SIGOUT signal with thethreshold TH2, the SIGOUT signal can be demodulated into the modulationsubject signal easily and precisely.

FIG. 9 illustrates the SIGIN signal to be output to the SIGIN line bythe processing unit 54 shown in FIG. 4.

The first part from the top in FIG. 9 illustrates an example of theSIGIN signal. As stated above, as in the modulation subject signalsupplied from the serial data switch 42 to the modulator 47, the SIGINsignal is a signal obtained by coding data into Manchester codes. Whenthe corresponding data indicates 0 (binary), the SIGIN signal changesfrom the L level to the H level, and when the corresponding dataindicates 1 (binary), the SIGIN signal changes from the H level to the Llevel.

As discussed above, the modulator 44 (FIG. 4) modulates the carrier byManchester codes. Accordingly, if the SIGIN signal, which is Manchestercodes, is sent from the message processor 14, the serial data switch 42can directly supply the SIGIN signal to the modulator 44 so that theSIGIN signal can be sent to an NFC device, such as the wirelesscommunication device 2, by near field communication.

More specifically, the second part from the top in FIG. 9 illustratesthe waveform of a current (modulated signal) flowing in the antenna 11when the SIGIN signal indicated in the first part from the top in FIG. 9is directly supplied to the modulator 44 and is used for modulatingelectromagnetic waves, which are the carrier, by the modulator 44.

A description is now given, with reference to FIG. 10, of wiredcommunication performed between the NFC interface 12 and the messageprocessor 14 shown in FIG. 4.

Upon receiving Manchester codes to be sent to the message processor 14from the demodulate processor 41 or the data processor 43, the serialdata switch 42 of the NFC interface 12 supplies the Manchester codes tothe modulator 47 as the modulation subject signal.

In step S1, the modulator 47 modulates the clock output from the clockselector 46 by the Manchester codes supplied from the serial data switch42 as the modulation subject signal, and sends the resulting modulatedsignal to the message processor 14 through the SIGOUT line as the SIGOUTsignal.

In step S11, the message processor 14 receives the SIGOUT signal sentfrom the modulator 47 of the NFC interface 12 through the SIGOUT line,and supplies the SIGOUT signal to the clock extracting unit 52 and thesignal extracting unit 53.

Then, in step S12, the clock extracting unit 52 extracts the clock fromthe SIGOUT signal, and the signal extracting unit 53 extracts theManchester codes from the SIGOUT signal as the modulation subjectsignal. The clock extracting unit 52 then supplies the extracted clockto the processing unit 54, and the signal extracting unit 53 thensupplies the extracted Manchester codes to the processing unit 54 as themodulation subject signal.

In step S13, the processing unit 54 processes the Manchester codessupplied from the signal extracting unit 53 in synchronization with theclock supplied from the clock extracting unit 52.

Then, in step S14, the processing unit 54 sends Manchester codes to besent to the NFC interface 12 to the NFC interface 12 through the SIGINline as the SIGIN signal.

In step S2, the serial data switch 42 of the NFC interface 12 receivesthe SIGIN signal, which are the Manchester codes sent from theprocessing unit 54 of the message processor 14 as described above, andsupplies the received SIGIN signal to the data processor 43 or themodulator 44.

If the Manchester codes as the SIGIN signal are supplied to the dataprocessor 43 from the serial data switch 42, the data processor 43decodes the Manchester codes into the original data, and supplies thedecoded data to the controller 13. If the Manchester codes as the SIGINsignal are supplied to the modulator 44 from the serial data switch 42,the modulator 44 modulates electromagnetic waves, which is the carrier,by using the Manchester codes, thereby sending the data corresponding tothe Manchester codes as the SIGIN signal to the NFC device thatgenerates the electromagnetic waves.

The modulator 47 continues sending the SIGOUT signal throughout wiredcommunication performed between the NFC interface 12 and the messageprocessor 14. Accordingly, if there is no data to be sent from the NFCinterface 12 to the message processor 14, the clock itself output fromthe clock selector 46 is sent to the message processor 14 from themodulator 47 as the SIGOUT signal.

As described above, ASK modulation is conducted on the clock by usingthe modulation subject signal (Manchester codes), and the SIGOUT signal,which is the resulting modulated signal, is sent to the messageprocessor 14 from the NFC interface 12 through the SIGOUT line.Accordingly, by sending the SIGOUT signal, both the data and the clockcan be sent from the NFC interface 12 to the message processor 14. Thatis, it is possible to send data and also supply a clock from the NFCinterface 12 to the message processor 14 by using a single connectingline, i.e., the SIGOUT line. This eliminates the need to connect the NFCinterface 12 and the message processor 14 by a connecting line dedicatedfor supplying a clock from the NFC interface 12 to the message processor14.

It would be possible that, instead of supplying a clock from the NFCinterface 12 to the message processor 14, a clock generator similar tothe clock generator 45 (FIG. 4) be contained in the message processor 14so that the message processor 14 can be operated in synchronization witha clock generated by the built-in clock generator.

In this case, however, it is necessary to integrate a quartz oscillatorfor generating a clock into the clock generator, which increases thesize of the message processor 14.

If the message processor 14 is formed as a SIM card or a UIM card, itshould be formed as a small device since a SIM card or a UIM card issmall, as stated above. Thus, integrating a clock generator into themessage processor 14 is not suitable.

It is thus necessary to supply a clock to the message processor 14 froman external source. However, if a clock is independently supplied to themessage processor 14, a terminal to be connected to a line dedicated forsupplying a clock should be provided for the message processor 14.

However, if the message processor 14 is formed as a SIM card, as statedabove, it is desirable that the number of lines to be connected to theSIM card be minimized since the number of terminals provided for the SIMcard is limited.

As discussed above, ASK modulation is conducted on the clock by usingthe modulation subject signal (Manchester codes), and the resultingmodulated signal is sent to the message processor 14 from the NFCinterface 12 through the SIGOUT line as the SIGOUT signal. Thiseliminates the need to provide a connecting line dedicated for supplyinga clock from the NFC interface 12 to the message processor 14. As aresult, the NFC interface 12 and the message processor 14 can beconnected to each other with a minimum number of connecting lines.

Additionally, since the SIGOUT signal is a signal obtained by performingASK modulation on the clock, the rising edges (positive edges) and thefalling edges (negative edges) can be maintained as they are althoughthe levels thereof are different. Accordingly, the message processor 14can easily extract the clock having a duty ratio of 50 merely bycomparing the SIGOUT signal with a predetermined threshold.

Since the SIGOUT signal contains data (Manchester codes) havingdifferent levels, the message processor 14 can easily extract the databy detecting the envelope of the SIGOUT signal and by comparing theenvelope with a predetermined threshold.

That is, the message processor 14 can extract the clock and data fromthe SIGOUT signal with a simple circuit configuration.

Thus, wired communication can be performed between the NFC interface 12that can perform both wireless communication and wired communication,such as a communication interface for an IC card, and the messageprocessor 14 that performs wired communication, such as a SIM card, by asimple configuration of the devices (circuit) by minimizing the numberof lines for connecting the NFC interface 12 and the message processor14.

According to NFCIP-1, data can be sent at various transmission rates,such as 106 kbps, 212 kbps, and 424 kbps. Whichever transmission rate isused for performing ASK modulation on a clock by data (Manchestercodes), the circuit configuration of the NFC interface 12 and themessage processor 14 remains the same. That is, it is not necessary tochange the circuit configuration of the NFC interface 12 and the messageprocessor 14 depending on the transmission rate.

The SIGIN signal sent from the message processor 14 to the NFC interface12 is Manchester codes, i.e., a signal obtained by coding data by acoding method which is used when performing wireless communicationbetween the NFC interface 12 and an NFC device. This allows the NFCinterface 12 to modulate electromagnetic waves, which are a carrier, byusing the SIGIN signal sent from the message processor 14 as it is andto send the modulated signal to the NFC device.

Signals sent and received by the NFC interface 12 by wirelesscommunication are signals obtained by performing ASK modulation on acarrier by using Manchester codes (modulation subject signal). Incontrast, the SIGOUT signal is a signal obtained by performing ASKmodulation on a clock by using Manchester codes, and the SIGIN signal isManchester codes. Accordingly, the compatibility of signals sent andreceived by the NFC interface 12 by wireless communication with theSIGOUT signal and the SIGIN signal sent and received between the NFCinterface 12 and the message processor 14 is high. Thus, it is notdifficult to integrate the circuit of an existing NFC device into themessage processor 14. More specifically, an existing NFC device is, forexample, an IC card, and the IC card includes, not only an NFC interfacesimilar to the NFC interface 12, but also a tamper-resistant SAM thatmanages cryptographic keys for conducting authentication or encryptingdata. That SAM can be easily integrated into the message processor 14.

Additionally, the SIGIN line used for sending data (SIGIN signal) fromthe message processor 14 to the NFC interface 12 and the SIGOUT lineused for sending data (SIGOUT signal) from the NFC interface 12 to themessage processor 14 are physically different connecting lines.Accordingly, the NFC interface 12 and the message processor 14 can bedesigned without precisely taking impedance changes into consideration,which would otherwise be necessary when sending signals from acommunication interface to a SIM card and vice versa by using a singleline, as discussed above. As a result, wired communication can becomemore stable.

In the above-described embodiment, as the communication device that canperform both wired communication and wireless communication, the NFCinterface 12, which serves as a communication interface performingwireless communication according to NFCIP-1, is used. However, anothercommunication interface performing wireless communication according tothe standards other than NFCIP-1 may be used.

Additionally, although in this embodiment the message processor 14,which serves as a wired communication device, is formed as a SIM card ora UIM card, it may be configured as another type of device.

The foregoing embodiment has been described in the context of acommunication system including a cellular telephone. However, this is anexample only, and the present disclosure is applicable to a device thatcan integrate therein a communication interface that can perform bothwireless communication, in particular, near field communication, andwired communication.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A communication system comprising: a communication device; and awired communication device connected to the communication device by afirst connecting line and a second connecting line; the communicationdevice including: (a) a first processor; (b) a first memory devicestoring first instructions, which when executed by the first processorcause the first processor to: (i) output a clock; (ii) generate aresulting modulated signal by performing amplitude shift keyingmodulation on the clock using a modulation subject signal to be sent tothe wired communication device; (iii) output, via the first connectingline, the resulting modulated signal to the wired communication device;and (iv) communicate with a near field communication device thatperforms near field communication in at least one of an active mode anda passive mode, the near field communication device being different fromthe communication device and the wired communication device; the wiredcommunication device including: (a) a second processor; (b) at least oneof a subscriber identity module and a user identity module; and (c) asecond memory device storing second instructions, which when executed bythe second processor cause the second processor to: (i) extract theclock from the modulated signal sent from the first connecting line;(ii) extract the modulation subject signal from the modulated signalsent from the first connecting line; (iii) process the modulationsubject signal in accordance with the extracted clock; and (iv) output,via the second connecting line, the processed modulation subject signalto the communication device.
 2. The communication system of claim 1,wherein the first connecting line is physically different from thesecond connecting line.
 3. The communication system of claim 1, whereina cellular telephone includes the communication system.
 4. Thecommunication system of claim 1, wherein the modulation subject signalincludes Manchester codes.
 5. The communication system of claim 1,wherein the second instructions, when executed by the second processor,cause the second processor to process the modulated subject signal insynchronization with the extracted clock.
 6. The communication system ofclaim 1, wherein the second instructions, when executed by the secondprocessor, cause the second processor to extract the clock and themodulation subject signal by: (a) detecting an envelope of the resultingmodulated signal; and (b) comparing the envelope with a predeterminedthreshold.